1. Field of the Present Disclosure
This disclosure relates generally to power supplies for computers and other electronic devices, and more particularly to a DC power supply using rechargeable battery cells adapted for supporting input DC voltage requirements of microcomputers, personal computers and similar computer systems.
2. Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98
The need for alternative and backup power sources to standard power grid AC power has increased greatly over the last several years. With the proliferation of computers, such alternative power sources have become especially important. Due to evolving technologies and the abundance of features now available in a single electronic device, newer computers, televisions and other electronic systems often require several different, voltages and currents to operate. For instance, motherboards in today's new generation of personal computers require positive and negative 12 volts DC, positive and negative 5 volts DC and positive 3.3 volts DC. At this time, such voltages are provided by the computer's power supply, which conventionally steps down an input AC voltage to AC voltages equivalent to those required by the motherboard using transformers, then converts the AC voltages to the required positive and negative DC voltages using rectifiers, and then regulates the DC voltages and currents through regulator circuits.
In many instances, such power supplies are generally useful for their intended purposes. However, almost every computer user, at some time or another, has experienced a loss of data due to power interruptions. Such power interruptions gave rise to the current generation of backup power sources, most commonly known as uninterruptible power supplies or UPS for short battery backup systems.
UPS systems draw their energy from batteries and inverter circuitry converts the batteries' DC output voltage to an AC voltage, which is then supplied to a standard computer power supply to replace the unavailable line AC voltage. However, significant energy is lost to heat during the DC to AC conversion and the subsequent AC to DC conversion in the computer's power supply, resulting in a total power conversion efficiency of approximately fifty percent, and it also introduces unwanted transients which require additional filtering circuitry. As a result of this loss of efficiency, UPS systems, typically, can only operate for between ten and thirty minutes. Consequently, UPS systems are only intended as a short-term power source to give the user sufficient time to save the applications in use and shut down the computer. Line AC power, when available, is still intended to be the primary power source for this type of electronic equipment, as well as being necessary to recharge the UPS batteries.
Various other types of backup power sources have been developed over the years. However, virtually all of these prior art devices operate on the same principle as UPS systems, that is, during the presence of AC line power, the regular electronic device AC to DC power supply provides DC power to the computer, and when AC line voltage is absent or low, AC power is provided to the regular computer AC to DC power supply by backup batteries and DC to AC converters. Thus, such other prior art devices include many of the same limitations and problems discussed with respect to UPS systems and, consequently, are only able to operate for short periods of time.
Portable laptop computer batteries are an example of another common alternative power source. Such portable computers have become a mainstay for businessmen and other professionals and provide DC power when AC line voltage is absent. However, laptop computer power supplies also have certain inherent limitations which limit the batteries to approximately two hours of continuous operation without recharging and which render them inadequate as an alternative power source for present computers and electronic devices. Specifically, laptop computer batteries fail to directly provide the differential DC voltages required. Laptop batteries, typically, only provide a single output voltage, which must be converted or stepped down by the computer's circuitry to power the computer's components.
If the principals applied to laptop computers and their power systems were utilized for current computers, excessive power would be dissipated as heat, thereby requiring fans to maintain the power supply and surrounding computer components at a safe operating temperature. For example, as stated above, motherboards in current personal computers require positive and negative 12 volts DC, positive and negative 5 volts DC and positive 3.3 volts DC. During normal operation, the positive 5 volt line draws as much as 7 amps continuous and up to 10 amps during startup. Thus, in converting or stepping down the positive 12 volts to positive 5 volts, 49 watts of power is dissipated as heat. Consequently a greater amount of power is wasted in power conversion than is used by the motherboard. Such a waste of power is not only inefficient, but creates excessive heat and stress on computer components, thereby shortening their useful life.
Moreover, laptop computer batteries, like UPS systems, are intended to be only short-term backup power sources, and not replacements for AC power. Normal AC power, when available, is still intended to be the primary power source for laptop computers and is necessary to recharge its batteries.
Another prior art backup device which operates on similar principals to the laptop computer is shown in U.S. Pat. No. 5,578,876, which discloses a computer power system comprising an AC to DC power supply for providing DC power to the computer during the presence of AC line power and a backup power supply for providing DC power from batteries directly to the DC operated components, bypassing the AC to DC power supply, when AC line voltage is absent or low. Although improving over the previously described prior art devices by eliminating DC to AC conversion circuitry, this device still does not eliminate the loss of power and heat associated with regulator circuitry in typical power supplies and, consequently, includes some of the inherent design deficiencies of prior art power supplies. For instance, in providing DC power from batteries directly to the DC operated components, regulator circuitry is used to convert or step down the voltage from positive and negative 12 volts to the required lower positive and negative voltages. As discussed above, about fifty percent of the stored energy is dissipated as heat when providing positive 5 volts.
Applicant has discovered that a battery DC power supply which provides differential DC voltages directly from the batteries to the electronic equipment and which may serve as a primary power source in place of AC power supplies, as disclosed herein, eliminates or reduces many of the problems inherent in prior art power supplies.
The prior art, as evidenced by its generally consistent approach in power supply designs, teaches away from such a power supply and fails to recognize these problems. Consequently, there is no suggestion or motivation for one of ordinary skill in the art to modify any of the prior art devices in the manner disclosed by applicant's invention or in any other manner which might address these problems.
U.S. Pat. No. 5,959,370 to Pardo, Sep. 28, 1999, teaches a differential voltage battery DC power supply. However, the '370 reference fails to teach an arrangement of battery cells that is able to provide operating voltages without regulators and filtering circuitry. It also fails to teach recharging operation dependent on battery voltage fluctuation due to loss of charge and the use of the DC battery operation cut-in when mains current degrades or fails.
Accordingly, there is a need for a battery power supply capable of operation during the presence and also during the absence of AC line voltage, which reduces the inefficiencies, power loss and heat dissipation associated with the prior art power supply devices and which provides voltages directly from the batteries to the electronic device during the presence and absence of AC line voltage, thereby extending the operating time of the backup battery and the useful life of the electronic equipment's components. The use of a battery arrangement to provide the several voltages required by a computer system without the need for regulators and filtering networks clearly distinguishes over the prior art, most particularly, the Pardo references which teaches away from the present apparatus by the use of voltage regulators and transient filters. The present invention is particularly suited to overcome the problems described above.